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Abstract:

A panel filter is provided such as for HVAC applications in which one of
the cut edges is frayed and attached with adhesive to the inner
peripheral surface of a paper board frame. The frayed edges may
facilitate better gluing of pleated filter medium to the frame especially
for self-supported filter media applications and may increase structural
rigidity and sealibility as a whole. Frayed edges also provide
flexibility to assist in installation of a card of pleated filter medium
into a paper board frame.

Claims:

1. A panel filter, comprising: a rectangular frame having an inner
peripheral surface; a rectangular card of pleated filter medium extending
within the rectangular frame, the rectangular card having first and
second opposed edges, and third and fourth opposed edges extending
transversely relative to the first and second opposed edges; at least one
of said edges being a frayed edge and attached with adhesive to the inner
peripheral surface.

2. The panel filter of claim 1, wherein the first and second opposed
edges are formed at ends of pleats providing the first and second opposed
edges with a wavy pleated configuration, wherein each of the first and
second opposed edges are frayed and attached with adhesive to the inner
peripheral surface.

3. The panel filter of claim 2, wherein the third and fourth edges are
linear and merely cut edges and unfrayed.

4. The panel filter of claim 1, wherein each frayed edges has a thickness
perpendicular into the pleated filter medium that is a distance of at
least 1 mm from a cut line of the frayed edge.

5. The panel filter of claim 1, wherein each frayed edges has a thickness
perpendicular into the pleated filter medium that is a distance of at
least 3 mm from a cut line of the frayed edge.

6. The panel filter of claim 1, wherein the pleated filter medium is a
self supporting pleated filter medium having pleats that are sufficiently
stiff and self supporting to maintain pleated form during passage of
fluid when in use.

7. The panel filter of claim 6, wherein the self supporting pleated
filter medium comprises a multi-component filtration fibers including a
low melt component and a high melt component having a higher melting
temperature than the low melt component, the low melt component being in
a post-melted state binding fibers of the together, wherein at the
binding of the low melt component is substantially broken at the at least
one of said edges being frayed.

8. The panel filter of claim 2, wherein the adhesive wicks into each
frayed edge and wherein the frayed edge prior to application of adhesive
is relatively flexible compared to the sufficiency stiff nature of the
pleats.

9. The panel filter of claim 8, wherein adhesive lines the inner
peripheral surface of the frame, and wherein the frame includes integral
webbing bonded to pleat tips of the pleats along a first face of the
panel filter; and further comprising support strips bonded to pleat tips
of the pleats along a second face of the panel filter opposite said first
face.

10. The panel filter of claim 1, wherein the frame is paperboard material
and sized and configured for an HVAC system.

11. A method of forming a panel filter, comprising: cutting a span of
filter medium to have opposed cut edges; fraying the opposed cut edges;
and pleating the span of filter medium.

12. The method of claim 11, further comprising: cutting the filter medium
periodically transversely to said cutting a span to create rectangular
cards of pleated filter medium; arranging the pleated filter medium in a
rectangular frame; and adhesively attaching the frayed opposed cut edges
to the frame.

13. The method of claim 12, further comprising bonding pleat tips on
opposed faces of the pleated filter medium to webbing or strips extending
over each of the opposed faces.

14. The method of claim 11, wherein said fraying comprises driving
brushes on the opposed cut edges with the brushes engaging at least 1 mm
of the cut edge.

15. The method of claim 14, further comprising vacuuming fiber debris
generated by the driving of the brushes against the cut edges.

16. The method of claim 11, wherein the pleating is subsequent to said
fraying.

Description:

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

[0001] This patent application claims the benefit of U.S. Provisional
Patent Application No. 61/428,149, filed Dec. 29, 2010, the entire
teachings and disclosure of which are incorporated herein by reference
thereto.

FIELD OF THE INVENTION

[0002] The present invention pertains generally to pleated air filters and
more particularly, pleated panel filters in which a rectangular card of
pleated filter medium is secured within a rectangular frame and the means
by which securement of the rectangular card of pleated filter medium is
secured within such a rectangular frame.

BACKGROUND OF THE INVENTION

[0003] One common form of pleated air filters is known as a panel filter
in which a rectangular card of pleated filter medium is secured within a
rectangular paper board frame (e.g. such as fiberboard or cardboard). One
common use for such panel filters is in HVAC systems for homes and other
buildings where heating, ventilation and/or air conditioning is desired.
Because such pleated panel filters are typically low cost disposable
items, it is highly desirable to produce such pleated air filters using
automated machinery and automated processes which allow manufacturing
costs of the filter to be minimized.

[0004] Additionally, it is known that the porous filter media which is
formed into a pleated accordion like structure may be "self supporting"
as disclosed, for example, in U.S. Patent Publication No. 2006/0283162 to
Dent et al; and U.S. Pat. Nos. 7,255,723 to Choi et al.; 7,156,891 to
Winters et al.; and U.S. Pat. No. 6,254,653 to Choi et al. the entire
disclosures of these four patent publications is hereby incorporated by
reference in their entireties. For example, one form of a self supporting
pleated filter medium comprises a multi-component filtration fibers
including low melt components and high melt components that have higher
melting temperature than the low melt component. In these arrangements,
the low melt component is partially melted to a glassy or partially
liquefied state and serves to bind the high melt fibers together, thus
forming a heat set into the pleats of the pleated filter medium. As a
consequence, this filter medium known as self-supporting pleated filter
medium, tends to be relatively stiff in nature as compared to other
filtration mediums that do not include such a stiffening binder
component. Self-supporting pleated filter medium may also include other
forms of adhesives or the like within the fibers to provide such a
relatively stiff character to pleated filter media card so that while in
use, the filter medium is sufficiently stiff and self-supporting to
maintain the pleated form when subjected to passage of fluid such as a
forced air flow of HVAC systems in buildings. An advantage of such
self-supporting media is that wire scrims that may be co-pleated to
provide the support for such pleated filter medium may be eliminated or
at least reduced in structure. The amount of other external supports to
the filter medium can be thus reduced.

[0005] While self-supporting pleated filter medium has provided an advance
in the art, it is not without its drawbacks in that the relatively stiff
nature can pose difficulties. The present invention is directed towards
improvements that are particularly advantageous to such self-supporting
pleated panel filter elements and can be applied to those embodiments
such as described in the above incorporated by reference patent
publications or to other such self-supporting applications, and even
potentially to other non self-supporting pleated filter element
applications.

BRIEF SUMMARY OF THE INVENTION

[0006] The present invention is generally directed toward improvements
relative to the glue interface between the rectangular card of pleated
filter medium and the inner peripheral surface of the rectangular frame
where adhesive is conventionally used to attach one or more edges of the
pleated filter medium to the inner peripheral surface of the rectangular
frame. More specifically, at least one of the edges of the pleated filter
medium is a frayed edge and attached with adhesive to the inner
peripheral surface of the rectangular frame.

[0007] One or more advantages may flow from this arrangement. For example,
the frayed edge provides a more flexible surface that allows easier
insertion and positioning within the rectangular frame. The frayed edge
is more receptive to adhesive and can even act to wick adhesive. A better
or structurally more rigid structure may form as a result of glue wicking
into the frayed edge converting a flexible structure to a more rigid
structure once wicked and cured. Also, better interface sealing may
result due to the flexible characteristic of the frayed edge and
resilient nature of the media, which presses it into better engagement
with the inner peripheral surface of the frame and the adhesive carried
there along. Embodiments of the present invention may be used for any of
these advantages or for other reasons as may be desired.

[0008] A panel filter in accordance with an aspect of the invention,
therefore, comprises a rectangular frame having an inner peripheral
surface. A rectangular card of pleated filter medium extends within the
rectangular frame. The rectangular card has first and second opposed
edges and a third and fourth opposed edges extending transversely
relative to the first and second opposed edges. At least one of the edges
is a frayed edge and attached with adhesive to the inner peripheral
surface of the rectangular frame.

[0009] Another inventive aspect is directed toward a method of forming
such a panel filter comprising: cutting a span of filter medium to have
opposed cut edges; and fraying the opposed cut edges. The span of a
filter media is pleated, preferably subsequent to the fraying. Also,
preferably, the fraying is conducted subsequent to the cutting, but may
be also performed simultaneously at the same time with a specialized
cutting die (e.g. such as a pinking type cutting device or other cutting
device that does not form a sharp cut edge, but rather frays the edge at
the same time).

[0010] Preferably, and according to one embodiment, the fraying comprises
driving brushes on opposed cut edges with brushes engaging at least one
millimeter of the cut edge and more preferably at least three millimeters
of the cut edge (typically up to about one-half centimeter). Adjustments
of the brushes can be made to engage more or less of the cut edge as may
be desirable and depending upon other parameters that may be used such as
the nature and amount of adhesives and the size. Fraying may also be
performed by any other roughening device.

[0011] Other aspects, objectives and advantages of the invention will
become more apparent from the following detailed description when taken
in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings incorporated in and forming a part of the
specification illustrate several aspects of the present invention and,
together with the description, serve to explain the principles of the
invention. In the drawings:

[0013] FIG. 1 is a schematic prospective view of the process for forming a
panel filter according to an embodiment of the present invention;

[0014] FIG. 2(A)-2(C) are perspective illustrations of a panel filter
element in accordance with an embodiment of the present invention with
FIG. 2(A) showing one inflow or outlet flow side of the filter, FIG. 2(B)
showing the other side opposite FIG. 2(A), and FIG. 2(C) showing a
rectangular card of pleated filter medium which is to be installed in a
rectangular frame;

[0015]FIG. 3 is an enlarged cross sectional view of a portion of the
panel filter showing the gluing interface between the pleated filter
medium and the paper board frame; and

[0016]FIG. 4 is a perspective illustration of a frame assembly structure
including brush fray heads engaging opposing sides of self-supporting
filter medium; the filter medium being run along a line prior to a
scoring and pleating station;

[0017]FIG. 5 and FIG. 6 are pictures showing a rectangular card of
pleated filter medium having opposed edges with a wavy, pleated
configuration that have been frayed in accordance with an embodiment of
the present invention.

[0018] While the invention will be described in connection with certain
preferred embodiments, there is no intent to limit it to those
embodiments. On the contrary, the intent is to cover all alternatives,
modifications and equivalents as included within the spirit and scope of
the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

[0019] In accordance with an embodiment of the present invention, FIG.
2(A)-2(C) illustrate a rectangular panel filter 10 having at least one
frayed edge 12 of filter medium. The frayed edge 12 can belt to
facilitate gluing attachment as shown, for example, in FIG. 3 with the
frayed edges being shown in photographic detail in FIG. 5 and FIG. 6.

[0020] Panel filter 10 includes a rectangular frame 16 which is preferably
of paper board material such as cardboard, paper, fiber material or the
like. The frame 16 has an inner peripheral surface 18 that extends around
the inner periphery of the frame 16. Adhesive 20 is applied preferably to
the entire peripheral surface 16 and thereby lines the entire rectangular
inner peripheral surface 18 of the frame. The adhesive 20 is used to
secure a rectangular card 22 of pleated filter medium 24 within the
rectangular frame 16.

[0021] As shown, the card of pleated filter medium includes leading and
trailing cut lineal edges 20; and also opposed pleated wavy edges 28 that
extend transversely relative to the lineal edges 26. In particular, it
can be seen that the wavy edges are formed at the ends of individual
pleats with pleat flanks 30 providing these opposed edges with a wavy
pleated configuration. The wavy configuration is meant to include
different types of pleat tips 38 including pointed pleats or flattened
pleats as may be used such, as for example, demonstrated by the
aforementioned referenced patents.

[0022] As shown, each of the wavy edges 28 are frayed and attached via the
adhesive 20 to the inner peripheral surface 18 of the frame 16.

[0023] While the lineal edges 26 may also be frayed, the straightness of
these structures allow the lineal edges 26 to have better contact,
especially considering part of the end flanks may be available for gluing
and considering the flexibility afforded in the direction of pleating. As
such, lineal edges 26 may be merely cut edges and unfrayed unlike the
wavy edges 28. Alternatively, lineal edges 26 may additionally or
alternatively be frayed.

[0024] Preferably, each of the frayed edges 12 has a thickness
perpendicular to the pleated medium (thickness designated T) that is at
least one millimeter from a cut line 34 of the frayed edge and more
preferably at least three millimeters from the cut line 34 of the frayed
edge 12. Preferably, it may be up to or around one-half centimeter but
preferably, not more than one centimeter.

[0025] The frayed edges 12 are particularly advantageous where the pleated
filter medium is a self-supporting pleated filter medium 24 that has
individual pleats with pleat flanks 30 that are sufficiently stiff and
self-supporting to maintain the pleated form during forced air flow when
in use such as in an HVAC system in which forced air is blown through the
filter such as in a building.

[0026] The self-supporting pleated filter medium may comprise a
multi-component filtration fibers (often referred to as bicomponent)
including the low melt component in a high melt component that has a
higher melting temperature than the low melt component. The low melt
component in a post melted state binds the fibers together and thereby
provides the relative stiffness into the pleat planks 30. However, as
depicted in FIG. 3 and as can also be seen with reference to FIG. 5 and
FIG. 6, the binding of the low melt component is substantially broken at
the frayed edges 12.

[0027] It can also be seen in FIG. 3 that the adhesive 20 tends to wick
into each of the frayed edge. Further, as can be appreciated, the frayed
edge due to the substantially breaking of the binding provided by the low
melt component is relatively flexible as compared to the more stiff
nature of the pleats. This facilitates more easy insertion of the card 22
into the panel filter frame 16 during assembly. With the adhesive 20
extending around the entire inner peripheral surface 18 of the frame 16,
the adhesive 20 serves to sealingly bond and substantially prevent leak
passages between the pleated filter medium 24 and the frame 16. Further,
with the adhesive 20 attending to wick into the frayed edges 12 an even
stiffer structure once assembled may be provided in some embodiments if
sufficient adhesive is present due to the fact that the adhesive once
cured provides binding and structural strength. Further, the frayed edges
12 due to the increased flexibility may be sized slightly greater than
the rectangular inner peripheral surface 18 such that once the card 22 is
inserted, it may easily bend and thereby engage with the inner peripheral
surface and provide for increased gluing surface between the frame 16 and
the card 22 of pleated filter medium also providing structural strength
and increased sealability.

[0028] The frame and support structure provided by the frame may take
various forms such as disclosed in the aforementioned patents which have
been incorporated by reference. For example, in one embodiment, the frame
16 includes integral webbing 36 that has adhesive applied thereto (such
as glue or hot melt) and which is bonded to pleat tips 38 (either pointed
or flattened pleat tips) along a first face 40 of the panel filter 10.
Further, as shown, for example in FIG. 2(C), prior to assembly and FIG.
2(B) once assembled a plurability of support strips 42 (which may also be
formed similarly from paper board material) are bonded with adhesive such
as hot melt or glue to the pleat tips 38 along a second face 44 of the
panel filter 10 opposite the first phase. One of the first and second
faces may form the inlet face while the other forms the outlet face or it
may be interchangeable either way. Typically, the frame is paper board
and size and configured for an HVAC system of a building.

[0029] Turning to FIG. 1 and FIG. 4, methods and manufacturing equipment
are illustrated. As shown therein, cut filter medium 24 prior to pleating
is being advanced along a manufacturing line 48 such as being unwound
from a roll of filter media (not shown). The roll of filter media may
already have been cut to provide the cut line 34 or alternatively an
upstream splicing station may be used to trim and thereby cut the filter
media to the desired width. In either event, the span of filter medium is
cut to have opposed cut edges. Also illustrated, is that rotating fraying
brushes 50 are used and employed to engage the opposed cut edges at cut
line 34 thereby forming frayed edges 12. In this embodiment, fraying is
accomplished by opposed rotating brushes which engage upon and act on
opposed cut sides of the filter medium 24 which is being moved along the
manufacturing line 48. Thereafter, the media may be moved through a
scoring station 52 and a pleating station 54 which are effective to fold
the media into a pleated accordion like fashion as it is moved along the
manufacturing line. Thereafter, and to hold the spacing of the pleats,
lineal support strips 42 are applied and glued to the pleat tips 38.
Thereafter, at a cutting station 56, the cards 22 of pleated filter
medium 24 are cut. From there, the individual cards 22 of pleated filter
medium 24 can be adhesively attached into a frame having adhesive lining
the inner peripheral surface thereof.

[0030] While one embodiment is shown for performing the fraying 50, it
will be appreciated that other suitable means may also perform the
fraying. For example, a splicing head may be used to simultaneously cut
and fray the opposed cut edges at the same time and are, therefore,
covered by embodiments of the present invention. For example, the cutting
head may include a pinking type head to provide its own wavy pattern
along the cut edges where additional compression or engagement with the
splicing device may fray rather than provide a sharp cut. More
preferably, subsequent engagement of the cut edge such as through a
fraying, brush or simple engagement of the cut edges being moved against
a stationary surface or brush may be employed to reduce the binding
provided by the low melt component of the filter medium. Belts, sanders,
or other devices may alternatively be used as the fraying means as well.
Further, while pleating is shown subsequent to the fraying and is
preferred, it is also possible to fray the edges during or after the
pleating step with the same means.

[0031] As show in FIG. 4, an assembly 58 is illustrated for facilitating
the fraying of the cut edges. As shown therein, motors 60 supported on
opposing sides is a port head chasis 62 drive and rotate fraying brushes
50 in engagement with the opposed cut edges of the filter medium 24 being
moved along the manufacturing line 48. A screw 64 can move opposed
carriages 66 of the support head chassis 62 toward and away from each
other to thereby adjust how much fraying is conducted against the cut
edges and to accommodate different widths of filter media. Guides 68 also
surround the edges and have an opening 60 to support and align the
opposed edges of the filter medium relative to the fraying brushes 50.
Additionally, a vacuum 72 is provided on each slide and approximate to
each fraying brush 50 (only one side being illustrated in FIG. 4). From
that, any debris or fibers generated due to the fraying can be sucked out
and eliminated from the internal manufacturing environment.

[0032] All references, including publications, patent applications, and
patents cited herein are hereby incorporated by reference to the same
extent as if each reference were individually and specifically indicated
to be incorporated by reference and were set forth in its entirety
herein.

[0033] The use of the terms "a" and "an" and "the" and similar referents
in the context of describing the invention (especially in the context of
the following claims) is to be construed to cover both the singular and
the plural, unless otherwise indicated herein or clearly contradicted by
context. The terms "comprising," "having," "including," and "containing"
are to be construed as open-ended terms (i.e., meaning "including, but
not limited to,") unless otherwise noted. Recitation of ranges of values
herein are merely intended to serve as a shorthand method of referring
individually to each separate value falling within the range, unless
otherwise indicated herein, and each separate value is incorporated into
the specification as if it were individually recited herein. All methods
described herein can be performed in any suitable order unless otherwise
indicated herein or otherwise clearly contradicted by context. The use of
any and all examples, or exemplary language (e.g., "such as") provided
herein, is intended merely to better illuminate the invention and does
not pose a limitation on the scope of the invention unless otherwise
claimed. No language in the specification should be construed as
indicating any non-claimed element as essential to the practice of the
invention.

[0034] Preferred embodiments of this invention are described herein,
including the best mode known to the inventors for carrying out the
invention. Variations of those preferred embodiments may become apparent
to those of ordinary skill in the art upon reading the foregoing
description. The inventors expect skilled artisans to employ such
variations as appropriate, and the inventors intend for the invention to
be practiced otherwise than as specifically described herein.
Accordingly, this invention includes all modifications and equivalents of
the subject matter recited in the claims appended hereto as permitted by
applicable law. Moreover, any combination of the above-described elements
in all possible variations thereof is encompassed by the invention unless
otherwise indicated herein or otherwise clearly contradicted by context.